Cocktail party effect
Encyclopedia
The cocktail party effect describes the ability to focus one's listening attention
on a single talker among a mixture of conversation
s and background noise
s, ignoring other conversations. The effect enables most people to talk
in a noisy place. For example, when conversing in a noisy crowded party, most people can still listen and understand the person they are talking with, and can simultaneously ignore background noise and conversations. Nevertheless, if someone calls out their name from across the room, people will sometimes notice (the "own name effect").
The auditory system can also switch the direction of attention and turn from one sound source to another.
The binaural aspect of the cocktail party effect is related to the localization of sound sources
. Experiments have shown that the auditory system is able to localize at least two sound sources simultaneously and assign the correct sound source characteristics to these sound sources simultaneously too. In other words, as soon as the auditory system has localized a sound source, it can extract the signals of this sound source out of a mixture of interfering sound sources.
It is assumed that the auditory system performs a kind of cross-correlation
function between both ear signals. A cross correlation function projects signals onto an axis, which corresponds to the time difference between both ear signals
. For example, sound with an interaural time difference of 0.3 ms is projected onto the 0.3 ms position of the correlation axis. If multiple sound sources are present, then complex correlation patterns appear. The statistical parameters of these patterns, like mean value and variance, depend on the directions and levels of the sound sources. The auditory system is obviously able to analyze these patterns and determine the signals of a dedicated sound source.
Attempts have been made to simulate the cocktail party effect by technical means. Cocktail party processors have been constructed which can extract the signal of a single sound source out of a mixture of sound sources. There are cocktail party processors, which are based on correlation functions, evaluating interaural time differences, but there are also cocktail party processors for interaural level differences. However, the principles of the human cocktail party effect are not yet fully investigated. Technical cocktail party processors do not yet reach the capabilities of the human auditory system.
The human pinna (the external flap of skin and cartilage of the ear) is a directionally-dependent filter that selectively removes particular frequencies, based on the direction from which sound comes. This filter can distinguish sounds from above vs. below, and from front vs. back, even when only a single ear is used.
lers. At that time, controllers received messages from pilots over loudspeakers in the control tower. Hearing the intermixed voices of many pilots over a single loudspeaker made the controller's task very difficult. The effect was first defined and named by Colin Cherry in 1953.
Cherry conducted attention
experiments in which subjects were asked to listen to two different messages from a single loudspeaker at the same time and try to separate them. His work reveals that our ability to separate sounds from background noise is affected by many variables, such as the gender
of the speaker, the direction from which the sound is coming, the pitch
, and the rate of speech.
Also during the 1950s, Broadbent conducted dichotic listening
experiments: subjects were asked to hear and separate different speech signals presented to each ear simultaneously (using headphones). From the results of his experiment, he suggested that "our mind can be conceived as a radio receiving many channels at once": the brain separates incoming sound into channels based on physical characteristics (e.g. perceived location), and submits only certain subsignals for semantic analysis (deciphering meaning). In other words, there exists a type of audio filter
in our brain that selects which channel we should pay attention to from the many kinds of sounds perceived. Broadbent proposed that the filter was hypothesized between the sensory buffer and short-term store (what is now called working memory) that prevents overloading memory. This is called Broadbent's filter theory. There is some empirical evidence to support this theory, though it has been criticized. There is evidence to suggest it is not just dependent on the physical characteristics of the stimulus. There are stimuli, such as someone calling your name, which will sometimes be processed. Treisman
(1960) found evidence to suggest that the filter just increases the threshold of an unattended stimulus, which sometimes can be processed if it is particularly important or has relevant meaning. Deutsch and Deutsch (1963) also offered an alternative to Broadbent's filter theory arguing for late selection depending on whether the stimulus needs to be responded to.
Since the human auditory system can localize and process several sound sources simultaneously, it has to decide, to which of these directions attention shall be paid. The Franssen effect
gives some information about how the auditory system works and where the limitations are.
Therefore the auditory system can only localize a sound source if the directional information is reliable (like at the onset of a specific sound). If no reliable directional information is available, the auditory system seems to hold the last information as long as no better information is available:
The cocktail party effect can occur both when we are paying attention to one of the sounds around us and when it is invoked by a stimulus
which grabs our attention suddenly.
This phenomenon is still very much a subject of research, in humans as well as in computer implementations (where it is typically referred to as source separation
or blind source separation). The neural mechanism in human brains is not yet fully clear.
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
on a single talker among a mixture of conversation
Conversation
Conversation is a form of interactive, spontaneous communication between two or more people who are following rules of etiquette.Conversation analysis is a branch of sociology which studies the structure and organization of human interaction, with a more specific focus on conversational...
s and background noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
s, ignoring other conversations. The effect enables most people to talk
Talk
Talk may refer to:* Conversation, interactive communication between two or more people* Speech, the production of a spoken language* Interaction, face to face conversations-Software:* Google Talk, a Windows- and web-based instant messaging program...
in a noisy place. For example, when conversing in a noisy crowded party, most people can still listen and understand the person they are talking with, and can simultaneously ignore background noise and conversations. Nevertheless, if someone calls out their name from across the room, people will sometimes notice (the "own name effect").
The auditory system can also switch the direction of attention and turn from one sound source to another.
Binaural processing
The cocktail party effect works best as a binaural effect, which requires hearing with both ears. Persons with only one functional ear are much more disturbed by interfering noise than people with two healthy ears.. However, even without binaural location information, people can, even if with greater difficulty, selectively attend to one particular speaker if the pitch of their voice or the topic of their speech is sufficiently distinctive.The binaural aspect of the cocktail party effect is related to the localization of sound sources
Sound localization
Sound localization refers to a listener's ability to identify the location or origin of a detected sound in direction and distance. It may also refer to the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space .The sound localization mechanisms of the...
. Experiments have shown that the auditory system is able to localize at least two sound sources simultaneously and assign the correct sound source characteristics to these sound sources simultaneously too. In other words, as soon as the auditory system has localized a sound source, it can extract the signals of this sound source out of a mixture of interfering sound sources.
It is assumed that the auditory system performs a kind of cross-correlation
Cross-correlation
In signal processing, cross-correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them. This is also known as a sliding dot product or sliding inner-product. It is commonly used for searching a long-duration signal for a shorter, known feature...
function between both ear signals. A cross correlation function projects signals onto an axis, which corresponds to the time difference between both ear signals
Interaural time difference
The interaural time difference when concerning humans or animals, is the difference in arrival time of a sound between two ears. It is important in the localisation of sounds, as it provides a cue to the direction or angle of the sound source from the head. If a signal arrives at the head from one...
. For example, sound with an interaural time difference of 0.3 ms is projected onto the 0.3 ms position of the correlation axis. If multiple sound sources are present, then complex correlation patterns appear. The statistical parameters of these patterns, like mean value and variance, depend on the directions and levels of the sound sources. The auditory system is obviously able to analyze these patterns and determine the signals of a dedicated sound source.
Attempts have been made to simulate the cocktail party effect by technical means. Cocktail party processors have been constructed which can extract the signal of a single sound source out of a mixture of sound sources. There are cocktail party processors, which are based on correlation functions, evaluating interaural time differences, but there are also cocktail party processors for interaural level differences. However, the principles of the human cocktail party effect are not yet fully investigated. Technical cocktail party processors do not yet reach the capabilities of the human auditory system.
Monaural processing
The auditory system does not only use methods for a direction specific signal processing, it also uses monaural effects for noise reduction. If the characteristics of a desired signal are known (like the characteristics of speech) or can be estimated (like expected phonemes at observed mouth movements), then all signal components which do not match the expected characteristics can be suppressed and the disturbing effect of this noise can be reduced.The human pinna (the external flap of skin and cartilage of the ear) is a directionally-dependent filter that selectively removes particular frequencies, based on the direction from which sound comes. This filter can distinguish sounds from above vs. below, and from front vs. back, even when only a single ear is used.
Control of the direction of attention
In the early 1950s much of the early work in this area can be traced to problems faced by air traffic controlAir traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
lers. At that time, controllers received messages from pilots over loudspeakers in the control tower. Hearing the intermixed voices of many pilots over a single loudspeaker made the controller's task very difficult. The effect was first defined and named by Colin Cherry in 1953.
Cherry conducted attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
experiments in which subjects were asked to listen to two different messages from a single loudspeaker at the same time and try to separate them. His work reveals that our ability to separate sounds from background noise is affected by many variables, such as the gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...
of the speaker, the direction from which the sound is coming, the pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...
, and the rate of speech.
Also during the 1950s, Broadbent conducted dichotic listening
Dichotic listening
In cognitive psychology, dichotic listening is a procedure commonly used to investigate selective attention in the auditory system. In dichotic listening, two different auditory stimuli are presented to the participant simultaneously, one to each ear, normally using a set of headphones...
experiments: subjects were asked to hear and separate different speech signals presented to each ear simultaneously (using headphones). From the results of his experiment, he suggested that "our mind can be conceived as a radio receiving many channels at once": the brain separates incoming sound into channels based on physical characteristics (e.g. perceived location), and submits only certain subsignals for semantic analysis (deciphering meaning). In other words, there exists a type of audio filter
Audio filter
An audio filter is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications including graphic equalizers, synthesizers, sound effects, CD players and virtual reality systems.Being a frequency dependent...
in our brain that selects which channel we should pay attention to from the many kinds of sounds perceived. Broadbent proposed that the filter was hypothesized between the sensory buffer and short-term store (what is now called working memory) that prevents overloading memory. This is called Broadbent's filter theory. There is some empirical evidence to support this theory, though it has been criticized. There is evidence to suggest it is not just dependent on the physical characteristics of the stimulus. There are stimuli, such as someone calling your name, which will sometimes be processed. Treisman
Anne Treisman
Anne Marie Treisman FRS is a psychologist currently at Princeton University's Department of Psychology. She researches visual attention, object perception, and memory. One of her most influential ideas is the feature integration theory of attention, first published with G. Gelade in 1980...
(1960) found evidence to suggest that the filter just increases the threshold of an unattended stimulus, which sometimes can be processed if it is particularly important or has relevant meaning. Deutsch and Deutsch (1963) also offered an alternative to Broadbent's filter theory arguing for late selection depending on whether the stimulus needs to be responded to.
Since the human auditory system can localize and process several sound sources simultaneously, it has to decide, to which of these directions attention shall be paid. The Franssen effect
Franssen effect
The Franssen effect is an auditory illusion where the listener incorrectly localizes a sound. It was found in 1960 by Nico V. Franssen. There are two classical experiments, which are related to the Franssen effect, called Franssen effect F1 and Franssen effect F2.-Setup:There are two speakers to...
gives some information about how the auditory system works and where the limitations are.
Therefore the auditory system can only localize a sound source if the directional information is reliable (like at the onset of a specific sound). If no reliable directional information is available, the auditory system seems to hold the last information as long as no better information is available:
The cocktail party effect can occur both when we are paying attention to one of the sounds around us and when it is invoked by a stimulus
Stimulation
Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.The word...
which grabs our attention suddenly.
This phenomenon is still very much a subject of research, in humans as well as in computer implementations (where it is typically referred to as source separation
Source separation
Source separation problems in digital signal processing are those in which several signals have been mixed together and the objective is to find out what the original signals were. The classical example is the "cocktail party problem", where a number of people are talking simultaneously in a room ,...
or blind source separation). The neural mechanism in human brains is not yet fully clear.
See also
- Auditory processing disorderAuditory processing disorderAuditory Processing Disorder , also known as Central Auditory Processing Disorder is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. It is not a peripheral hearing disorder as individuals with APD usually have normal peripheral hearing...
- Auditory scene analysisAuditory scene analysisIn psychophysics, auditory scene analysis is the process by which the human auditory system organizes sound into perceptually meaningful elements. The term was coined by psychologist Albert Bregman...
- Cognitive scienceCognitive scienceCognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
- Echoic memoryEchoic memoryEchoic memoryis a type of sensory memory and auditory in nature; a component of sensory memory that is specific to retaining auditory information. Unlike visual memory, in which our eyes can scan the stimuli over and over, the auditory stimuli cannot be scanned over and over. Auditory stimuli is...
- Language processingLanguage processingLanguage processing refers to the way human beings process speech or writing and understand it as language. Most recent theories back the idea that this process is made completely by and inside the brain.- Spoken language :...
- King–Kopetzky syndrome
- Cocktail partyCocktail partyA cocktail party is a party where cocktails are served. Women may choose to wear what has become known as a cocktail dress.Although many believe the inventor of the cocktail party to be Alec Waugh of London, who in 1924 found a need for this pleasant interlude before a dinner party, an article in...
- Dream speechDream speechIn 1906 the famous German psychiatrist Emil Kraepelin published a monograph titled Über Sprachstörungen im Traume . In his psychiatry textbook Kraepelin used the shortcut Traumsprache to denote language disturbances occurring in dreams...
- Spatial hearing loss Spatial hearing lossSpatial hearing loss, also known as spatial processing deficit, refers to a form of deafness that is an inability to use spatial cues, i.e. where a sound originates from in space, to understand speech in the presence of background noise...
External links
- Audio examples of a cocktail party processor
- Handbook for acoustic ecology
- Dichotic Listening Experiment
- Early and Late Selection Theories of Attention by Nick Milton (May 1994)
- Neurofunctional studies in birds and bats
- A Primer on 'The cocktail party problem' by Prof. Josh McDermott in Current Biology
- http://www.rxpgnews.com/hearingimpairment/UK_researcher_identifies_brain_region_responsible__5036_5036.shtml